In the “Customizing UML” article, it is mentioned that the Ultra
heavyweight extension can removing an existing constraint, while in the
PPT “What_do_YOU_want_UML_to_be”, it said that the middleweight
extension can’t modify constraints. Could you illustrate it?

“As the open source project stands today, those OCL constraints would
not be executed at run-time. “Do you mean that currently there is no
effect for any addition of the OCL constraints while modeling or
metamodeling??